HTTP/2: send the output queue after emitting WINDOW_UPDATE.
HTTP/2: send the output queue after emitting WINDOW_UPDATE.

The WINDOW_UPDATE frame could be left in the output queue for an indefinite
period of time resulting in the request timeout.

This might happen if reading of the body was triggered by an event unrelated
to client connection, e.g. by the limit_req timer.

firebase/nginx,firebase/nginx,firebase/nginx,firebase/nginx